1. Field of the Invention
The present invention generally relates to a package structure, and more particularly to a three-dimensional package structure.
2. Description of the Prior Art
Increasing device complexity but shrinking size is common trend of electrical products. How to put more electrical elements or circuits into a limited space is important for electrical products' designers. Therefore, a three-dimensional package structure is a method to increase the density of the electrical products.
Point-of-Load (POL) converter also can be called as DC/DC converter. A conventional POL converter is packaged by BGA (Ball Grid Array) package or LGA (Land Grid Array) package.
As shown in FIG. 1, a conventional POL converter 1 includes at least one control device 11, at least one MOSFET 13 and a choke coil 15. Take BGA package for example. The control device 11 and the MOSFET 13 and the choke coil 15 are electrically connected to a substrate 17 having electrical circuits, such as printed circuit board, and then packaged to be a POL converter package structure by molding technology.
In the conventional package structure, the control device 11, the MOSFET 13, the choke coil 15, and other devices are disposed on the same horizontal surface of the substrate 17. Therefore, the surface occupied by the devices is pretty large. Moreover, packaging all devices on a single package structure has several disadvantages. For example, once any device inside the package structure is damaged, the whole package structure should be changed. Furthermore, during the operation of the choke coil 15, electric and magnetic are generated which can interfere with the operation of the control device 11. This phenomenon is termed electro-magnetic interference (EMI).